Solid-state battery and method for manufacturing a solid-state battery

Abstract

The present invention provides a solid-state battery and a method for manufacturing a solid-state battery, in which the junction between the negative electrode and the solid electrolyte layer is well maintained. [Solution] A solid-state battery comprising a negative electrode layer and a solid electrolyte layer adjacent to the negative electrode layer, wherein the negative electrode layer comprises a negative electrode active material and a solid electrolyte, and the negative electrode active material comprises a composite comprising a plurality of particles and particles not included in the composite, and at least a portion of the particles not included in the composite are invaginated into the solid electrolyte layer.

Description

[Technical Field]

[0001] This disclosure relates to a solid-state battery and a method for manufacturing a solid-state battery. [Background technology]

[0002] The practical application of rechargeable batteries that use a solid electrolyte (hereinafter also called solid-state batteries) is being considered as secondary batteries that can be used repeatedly by recharging. The electrodes of solid-state batteries may contain solid active material along with the active material to promote the movement of ions between particles of the active material within the electrode.

[0003] It is known that the negative electrode active material contained in the negative electrode of a secondary battery undergoes significant volume changes during battery charging (ion absorption) and battery discharging (ion release). Furthermore, it has been pointed out that repeated expansion and contraction of the negative electrode active material during charging and discharging alters the bonding state between the active material particles and the solid electrolyte within the negative electrode, which can cause battery degradation. As a measure to suppress the volume change of the negative electrode active material associated with the charging and discharging of batteries, it has been proposed to coat the surface of the negative electrode active material with a sulfide solid electrolyte (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-128857 [Overview of the project] [Problems that the invention aims to solve]

[0005] Solid-state batteries have a layer containing a solid electrolyte (hereinafter also referred to as the solid electrolyte layer) placed between the positive electrode and the negative electrode. The solid electrolyte layer serves as a separator that isolates the positive electrode and the negative electrode, and as a pathway for ions to move between the positive electrode and the negative electrode. Changes in the junction state between the negative electrode and the solid electrolyte layer have been identified as a factor contributing to the increase in resistance during charging and discharging of solid-state batteries. In view of the above circumstances, this disclosure aims to provide a solid-state battery and a method for manufacturing a solid-state battery in which the bonding state between the negative electrode and the solid electrolyte layer is well maintained. [Means for solving the problem]

[0006] The means for solving the above problems include the following embodiments. <1> It includes a negative electrode layer and a solid electrolyte layer adjacent to the negative electrode layer, The negative electrode layer comprises a negative electrode active material and a solid electrolyte. A solid-state battery in which the negative electrode active material comprises a composite containing a plurality of particles and particles not included in the composite, wherein at least a portion of the particles not included in the composite are invaginated in the solid electrolyte layer. <2> The negative electrode active material contains the element Si. <1> Solid-state batteries as described above. <3> The structure includes a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector arranged in this order on both sides of the positive electrode current collector. <1> or <2> Solid-state batteries as described above. <4> <1> ~ <3> A method for manufacturing a solid battery as described in any one of the items, The process involves forming a negative electrode layer on a solid electrolyte layer, which includes a negative electrode active material in the form of a composite of multiple particles and a solid electrolyte. A method for manufacturing a solid battery, comprising applying pressure to the negative electrode layer such that at least a portion of the particles contained in the composite separate from the composite, for the purpose of forming the negative electrode layer. <5> Forming positive electrode layers on both sides of the positive electrode current collector, Forming a solid electrolyte layer on the positive electrode layer, This includes, in this order, forming a negative electrode layer on the solid electrolyte layer, <4> A method for manufacturing a solid-state battery as described above. [Effects of the Invention]

[0007] According to the present disclosure, there are provided a solid-state battery in which a bonding state between a negative electrode and a solid electrolyte layer is maintained well, and a method for manufacturing the solid-state battery.

Brief Description of the Drawings

[0008] [Figure 1] It is a cross-sectional view schematically showing an example of a configuration of a negative electrode structure included in a solid-state battery. [Figure 2] It is a cross-sectional view schematically showing an example of a positive electrode center laminate structure included in a solid-state battery.

Embodiments for Carrying Out the Invention

[0009] Hereinafter, embodiments which are an example of the present disclosure will be described. These descriptions and examples are illustrative of the embodiments and do not limit the scope of the present disclosure.

[0010] In the present disclosure, a numerical range represented by "~" means a range including the numerical values described before and after "~" as a lower limit value and an upper limit value. In a numerical range described stepwise in the present disclosure, an upper limit value or a lower limit value described in one numerical range may be replaced with an upper limit value or a lower limit value of another numerically described stepwise range. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value of the numerical range may be replaced with the value shown in the examples. In the present disclosure, the amount of each component in a composition means the total amount of the plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified. In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment. In the present disclosure, the term "step" includes not only an independent step but also the term when the intended purpose of the step is achieved even when it cannot be clearly distinguished from other steps. In the present disclosure, the "solid-state battery" means a secondary battery that uses at least a solid electrolyte as an electrolyte. Therefore, the solid-state batteries of the present disclosure include batteries called by different names such as all-solid-state batteries and semi-solid-state batteries.

[0011] <Solid-state battery> One embodiment of the present disclosure is including a negative electrode layer and a solid electrolyte layer adjacent to the negative electrode layer, wherein the negative electrode layer includes a negative electrode active material and a solid electrolyte, the negative electrode active material includes a composite including a plurality of particles and particles not included in the composite, and at least a part of the particles not included in the composite are embedded in the solid electrolyte layer, which is a solid-state battery.

[0012] In the present disclosure, the negative electrode layer means a layer including at least a negative electrode active material, and the solid electrolyte layer means a layer including at least a solid electrolyte. In the following description, the structure composed of the negative electrode layer and the solid electrolyte layer adjacent to the negative electrode layer is also referred to as a "negative electrode structure".

[0013] FIG. 1 is a cross-sectional view schematically showing an example of the configuration of a negative electrode structure included in the solid-state battery of the present disclosure. As shown in FIG. 1, the negative electrode structure of the solid-state battery of the present disclosure includes a negative electrode layer 40 and a solid electrolyte layer 30 adjacent to the negative electrode layer 40. The negative electrode layer 40 includes particles 42 of a negative electrode active material and a solid electrolyte 44. The particles 42 of the negative electrode active material include a composite 42A including a plurality of particles and particles 42B not included in the composite. At least a part of the particles 42B not included in the composite are embedded in the solid electrolyte layer 30.

[0014] The negative electrode layer of a solid-state battery is generally press-treated at a high pressure in order to increase the density of the negative electrode layer and enhance the bonding strength between the negative electrode layer and adjacent layers (the solid electrolyte layer and the negative electrode current collector). As a result of the study by the present inventors, when a press treatment is performed on a negative electrode layer including negative electrode active material particles in the form of a composite composed of a plurality of particles, compared with the case where a press treatment is performed on a negative electrode layer including negative electrode active material particles that do not form a composite, it has been found that the bonding strength of the negative electrode layer to the solid electrolyte layer is improved. To investigate the cause, the interface between the negative electrode layer and the solid electrolyte layer was observed after a press treatment was performed on the negative electrode layer containing the composite negative electrode active material. As a result, it was observed that some of the particles separated from the composite had invaginated into the solid electrolyte layer. On the other hand, after pressing the negative electrode layer containing negative electrode active material particles that did not form a composite, no negative electrode active material particles invaginated into the solid electrolyte layer were observed at the interface between the negative electrode layer and the solid electrolyte layer. Based on the above, it is presumed that the improvement in bonding strength between the negative electrode layer and the solid electrolyte layer is due to the negative electrode active material particles embedded in the solid electrolyte layer.

[0015] The reason why particles separated from the composite material enter the solid electrolyte layer when a press treatment is applied to the negative electrode layer containing negative electrode active material particles in a composite state can be considered as follows, for example. Before the press treatment, a solid electrolyte surrounds the negative electrode active material particles within the negative electrode layer. Therefore, when the press treatment is performed, the solid electrolyte surrounding the negative electrode active material particles deforms and covers the surface of the negative electrode active material particles. As a result, it is thought that the invagination of the negative electrode active material particles into the solid electrolyte layer is suppressed. On the other hand, if the negative electrode active material contained in the negative electrode layer before the press treatment is performed is in a composite state, the press treatment will break down the composite, and some of the particles that formed the composite will separate from the composite. The particles immediately after being separated from the composite that has been broken down by the press treatment are not coated with solid electrolyte. Therefore, it is thought that the particles separated from the composite that are located near the interface with the solid electrolyte layer are in a state where they can easily invaginate into the solid electrolyte layer. In this disclosure, the pressing treatment performed on the negative electrode layer may be a treatment for transferring the negative electrode layer to the solid electrolyte layer, or a treatment performed on the negative electrode layer formed on the solid electrolyte layer.

[0016] In this disclosure, a composite comprising multiple particles includes a composite comprising multiple (e.g., 2 to 10) particles (primary particles). The composite may further include a binder for binding the primary particles together. The method for producing the anode active material in a composite state is not particularly limited and can be carried out by known methods. For example, the anode active material in a composite state can be produced by preparing a composition containing primary particles for forming a composite, a binder, and a solvent, forming this composition into droplets, and removing the solvent from the droplets. A composite containing multiple particles has voids within it. These voids within the composite have the effect of mitigating the volume change of the negative electrode active material.

[0017] The particle size of the composite of negative electrode active materials and primary particles contained in the negative electrode layer is not particularly limited. For example, the particle size of the composite can be selected from the range of 5 μm to 50 μm, and the particle size of the primary particles can be selected from the range of 0.5 μm to 5 μm. The material of the negative electrode active material contained in the negative electrode layer is not particularly limited. For example, it can be selected from the materials of the negative electrode active material described later. From the viewpoint of forming a state in which particles not included in the composite are invaginated into the solid electrolyte layer, it is preferable that the negative electrode active material is an active material containing the element Si. From the viewpoint of forming a state in which particles not included in the composite are invaginated into the solid electrolyte layer, it is preferable that the solid electrolyte layer contains a sulfide solid electrolyte.

[0018] The solid-state battery of this disclosure may include a plurality of negative electrode structures. The number of negative electrode structures included in the solid-state battery of this disclosure is not particularly limited and can be selected from, for example, 2 to 100.

[0019] If the solid-state battery of this disclosure includes multiple negative electrode structures, even if all of the negative electrode structures satisfy the above-described conditions (i.e., at least some of the particles not included in the composite present in the negative electrode layer are invaginated into the solid electrolyte layer), only some of the negative electrode structures may satisfy the above-described degree of orientation conditions. From the viewpoint of maintaining a good bonding state between the negative electrode layer and the solid electrolyte layer, it is preferable that 50% or more of the negative electrode structures included in the solid battery of this disclosure, based on the number, satisfy the above conditions, more preferably 70% or more of the negative electrode structures, based on the number, satisfy the above conditions, and even more preferably 80% or more of the negative electrode structures, based on the number, satisfy the above conditions.

[0020] (Example of a solid-state battery configuration) The solid-state battery of this disclosure may include a structure in which a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector are arranged in this order on both sides of the positive electrode current collector (hereinafter also referred to as a positive electrode center stacked structure).

[0021] An example of a positive electrode center stacked structure included in the solid-state battery of this disclosure is shown in Figure 2. As shown in Figure 2, the positive electrode center stacked structure 100 is arranged in the following order: first negative electrode current collector 50A, first negative electrode layer 40A, first solid electrolyte layer 30A, first positive electrode layer 20A, positive electrode current collector 10, second positive electrode layer 20B, second solid electrolyte layer 30B, second negative electrode layer 40B, and second negative electrode current collector layer 50B.

[0022] A solid-state battery having a positive electrode center stacked structure can be manufactured, for example, by a method including the steps shown below. In the following explanation, the first negative electrode layer and the second negative electrode layer may be referred to as the "negative electrode layer" without distinction, the first negative electrode current collector and the second negative electrode current collector may be referred to as the "negative electrode current collector" without distinction, the first positive electrode layer and the second positive electrode layer may be referred to as the "positive electrode layer" without distinction, the first positive electrode current collector and the second positive electrode current collector may be referred to as the "positive electrode current collector" without distinction, and the first solid electrolyte layer and the second solid electrolyte layer may be referred to as the "solid electrolyte layer" without distinction.

[0023] (Process 1) In step 1, positive electrode layers are formed on both sides of the positive electrode current collector to obtain a laminate 1 (layer structure: first positive electrode layer / positive electrode current collector / second positive electrode layer). The method for forming the positive electrode layers on both sides of the positive electrode current collector is not particularly limited and can be selected from coating methods, transfer methods, etc. Press treatment may be applied to the laminate 1 as needed. If necessary, end fillers may be placed at the ends of the positive electrode layers formed on both sides of the positive electrode current collector. The end fillers serve functions such as shaping the ends of the positive electrode layers and preventing the positive electrode layers from coming into contact with the negative electrode layers, which expand during charging. The material of the end fillers can be selected from electrically insulating materials such as resins.

[0024] (Process 2) In step 2, a solid electrolyte layer is formed on the positive electrode layer formed on both sides of the positive electrode current collector to obtain a laminate 2 (layer configuration: first solid electrolyte layer / first positive electrode layer / positive electrode current collector / second positive electrode layer / second solid electrolyte layer). The method for forming the solid electrolyte layer on the positive electrode layer is not particularly limited and can be selected from coating methods, transfer methods, etc. From the viewpoint of workability, a transfer method that can perform the formation of the solid electrolyte layer and the pressing process in one step is preferred.

[0025] (Step 3) In step 3, a negative electrode layer is formed on the solid electrolyte layer formed on the positive electrode layer to obtain a laminate 3 (layer structure: first negative electrode layer / first solid electrolyte layer / first positive electrode layer / positive electrode current collector / second positive electrode layer / second solid electrolyte layer / second negative electrode layer). The method for forming the negative electrode layer on the solid electrolyte layer is not particularly limited and can be selected from coating methods, transfer methods, etc. From the viewpoint of workability, a transfer method that can perform the formation of the negative electrode layer and the pressing process in one step is preferred.

[0026] (Step 4) In step 4, a negative electrode current collector is placed on the negative electrode layer formed on the solid electrolyte layer to obtain a laminate 4 (layer configuration: first negative electrode current collector / first negative electrode layer / first solid electrolyte layer / first positive electrode layer / positive electrode current collector / second positive electrode layer / second solid electrolyte layer / second negative electrode layer / second negative electrode current collector). If necessary, the laminate 4 may be subjected to a press treatment. If the negative electrode layer formed on the solid electrolyte layer in step 3 is in contact with the negative electrode current collector, step 4 can be omitted.

[0027] The negative electrode layer of a solid-state battery manufactured by the method including the above process is subjected to less pressure (during pressing or transfer) compared to the positive electrode layer. Therefore, the method including the above steps allows for sufficient pressure to be applied to the positive electrode layer to increase its density while controlling the pressure applied to the negative electrode layer to a desired degree. For this reason, solid-state batteries including a positive electrode center stacked structure tend to have an excellent balance of battery characteristics.

[0028] The negative electrode layer of a solid-state battery manufactured by the method including the above steps is formed on top of the solid electrolyte layer formed on top of the positive electrode layer in step 2. Therefore, when the negative electrode layer is formed in step 3, the solid electrolyte layer is in a state where negative electrode active material particles contained in the negative electrode layer are less likely to be imperforated by the pressure. In the solid-state battery of this disclosure, at least a portion of the negative electrode active material particles present in the negative electrode layer are invaginated into the solid electrolyte layer. Therefore, even when the solid-state battery is manufactured by a method including the above-mentioned steps (i.e., including a positive electrode center stacked structure), the bonding state between the negative electrode layer and the solid electrolyte layer is well maintained.

[0029] The following describes the components that make up the solid-state battery of this disclosure. In the following description, the negative electrode current collector and the positive electrode current collector may be referred to as "current collector" without distinction, the negative electrode layer and the positive electrode layer may be referred to as "electrode" without distinction, and the negative electrode active material and the positive electrode active material may be referred to as "electrode active material" without distinction.

[0030] (Current collector) The type of current collector included in the solid-state battery of this disclosure is not particularly limited and can be selected and used from known current collectors. Specifically, the material of the current collector may be a metal selected from Ag, Cu, Au, Al, Ni, Fe, and Ti, or an alloy containing these metals. In some embodiments of this disclosure, the positive electrode current collector may contain Al, and the negative electrode current collector may contain Cu. The thickness of the current collector is not particularly limited and can be selected considering the type and size of the battery obtained using the current collector. The thickness of the current collector may be, for example, 5 μm or more, 10 μm or more, or 20 μm or more. The thickness of the current collector may be, for example, 120 μm or less, 80 μm or less, or 60 μm or less.

[0031] (electrode layer) The electrode layer included in the solid-state battery of this disclosure contains at least an electrode active material and may optionally contain a binder, a conductive material, a solid electrolyte, etc. Examples of negative electrode active materials include carbon materials, active materials containing Si elements, metallic lithium, lithium-containing alloys, metals or alloys that can be alloyed with lithium, oxides, and transition metal nitrides. Examples of carbon materials include graphite materials, amorphous carbon materials, carbon black, and activated carbon. Examples of graphite materials include natural graphite and artificial graphite. Examples of amorphous carbon materials include hard carbon, soft carbon, coke, mesocarbon microbeads (MCMB), and mesophase pitch carbon fiber (MCF). Graphite materials may be coated with metal or amorphous carbon. Active materials containing the Si element include elemental silicon, silicon alloys (for example, alloys of Si with one or more metals selected from the group consisting of Sn, Ti, Fe, Ni, Cu, Co, and Al), porous silicon, silicon clathrate compounds, silicon oxides, and the like.

[0032] Specifically, examples of positive electrode active materials include composite oxides containing lithium and transition metals (hereinafter also referred to as composite oxides). Examples of composite oxides include composite oxides having a layered crystal structure, composite oxides having a spinel-type crystal structure, and composite oxides having an olivine-type crystal structure. Specific examples of composite oxides having a layered crystal structure include compounds represented as LiMO2 (where M is at least one transition metal selected from the group consisting of Ni, Co, and Mn), and compounds to which heterogeneous elements are added. Representative examples of composite oxides having a layered crystal structure include LCO (lithium cobaltate), NCM (lithium nickel-cobalt-manganate), and NCA (lithium nickelate or lithium nickel-cobalt-aluminate). LiMn2O4 is a specific example of a composite oxide having a spinel-type crystal structure. A specific example of a composite oxide having an olivine-type crystal structure is LiMPO4 (where M is Fe, Co, Ni, or Mn).

[0033] The electrode active material contained in the electrode layer may be a single type or a combination of two or more types. The electrode active material may take the form of, for example, fibers, spheres, flakes, etc. The volume-average particle size of the electrode active material may be selected from, for example, a range of 5 μm to 50 μm. The volume-average particle size of the electrode active material is defined as the value (D50) at which the cumulative amount from the smaller diameter side in the volume-based particle size distribution obtained using the laser diffraction-scattering method becomes 50%.

[0034] Examples of binders include polyvinylidene fluoride (PVdF), polyethylene, polypropylene, polyethylene terephthalate, cellulose, nitrocellulose, carboxymethylcellulose, polyethylene oxide, polyepichlorohydrin, polyacrylonitrile, styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), polyacrylate, polymethacrylate, and polytetrafluoroethylene (PTFE). The binder contained in the electrode layer may be a single type or a combination of two or more types.

[0035] Examples of conductive materials include carbon materials, metals, conductive oxides, and conductive nitrides. Specifically, carbon materials include graphite, carbon black (acetylene black, thermal black, furnace black, etc.), carbon nanotubes (CNTs), carbon nanofibers (CNFs), and vapor-grown carbon fibers (VGCFs). TM Examples include: The conductive material contained in the electrode layer may be a single type or a combination of two or more types.

[0036] Examples of solid electrolytes included in the electrode layer include sulfide solid electrolytes, oxide solid electrolytes, and polymer solid electrolytes. From the viewpoint of battery performance, sulfide solid electrolytes and polymer solid electrolytes are preferred as solid electrolytes, and from the viewpoint of thermal stability, sulfide solid electrolytes are more preferred. The solid electrolyte contained in the electrode layer may be a single type or a combination of two or more types.

[0037] Examples of sulfide solid electrolytes include compounds containing a metal element that acts as a conductive ion and sulfur (S). Examples of metallic elements include Li, Na, K, Mg, and Ca. Among these, Li is preferred as a metallic element. The sulfide solid electrolyte may contain Li and S, and at least one selected from the group consisting of P, Si, Ge, Al, and B. Among these, a sulfide solid electrolyte containing Li, S, and P (hereinafter also referred to as an LPS-type sulfide solid electrolyte) is preferred. From the viewpoint of ionic conductivity, sulfide solid electrolytes may contain halogen elements such as Cl, Br, and I. From the viewpoint of chemical stability, sulfide solid electrolytes may contain oxygen (O).

[0038] Specific examples of the LPS-type sulfide solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, LiBr-LiI-Li2S-P2S5, Li2S-P2S5-Z m S n (where m and n are positive numbers respectively, and Z is Ge, Zn or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers respectively, and M is P, Si, Ge, B, Al, Ga or In), etc.

[0039] In the above, the description of "Li2S-P2S5" means a sulfide solid electrolyte obtained by using Li2S and P2S5 as raw materials, and the same applies to other descriptions.

[0040] Among the LPS-type sulfide solid electrolytes, a sulfide solid electrolyte obtained by using Li2S and P2S5 is preferred, and a sulfide solid electrolyte satisfying the following formula is more preferred. Li 3+x+5y P 1-y S4(0 < x ≤ 0.6, 0 < y ≤ 0.2)

[0041] Examples of the oxide solid electrolyte include compounds having a NASICON (Na3Zr2PSi2O 12 )-type crystal structure. Compounds having a NASICON-type crystal structure have high ionic conductivity and excellent stability in the atmosphere. Examples of the compounds having a NASICON-type crystal structure include lithium-containing phosphates. Examples of the phosphates include composite lithium phosphate salts with Ti (for example, Li 1+x Al x Ti 2-x(PO4)3) Examples include compounds in which all or part of the Ti in the composite lithium phosphate salt is replaced with a tetravalent transition metal such as Ge, Sn, Hf, or Zr, or a trivalent transition metal such as Al, Ga, In, Y, or La. Specifically, examples of compounds having a NASICON-type crystal structure include Li-Al-Ge-PO-based materials (Li 1+x Al x Ge 2-x (PO4)3), Li-Al-Zr-PO material (Li 1+x Al x Zr 2-x (PO4)3), Li-Al-Ti-PO material (Li 1+x Al x Ti 2-x (PO4)3) are examples.

[0042] Examples of polymeric solid electrolytes include mixtures (complexes) of polymer compounds and electrolyte salts. Specific examples of polymer compounds include polyether-based polymer compounds such as polyethylene oxide (PEO) and polypropylene oxide (PPO), polyamine-based polymer compounds such as polyethyleneimine (PEI), and polysulfide-based polymer compounds such as polyalkylene sulfide (PAS). Among these, polyether-based polymer compounds are preferred.

[0043] (solid electrolyte layer) The solid electrolyte layer included in the solid battery of this disclosure includes a solid electrolyte. The type of solid electrolyte included in the solid electrolyte layer is not particularly limited and may be selected from the solid electrolytes that may be included in the electrode layer as described above. If the electrode layer contains a solid electrolyte, the solid electrolyte contained in the electrode layer and the electrolyte contained in the solid electrolyte layer may be the same or different. The solid electrolyte layer may contain only one type of solid electrolyte or a combination of two or more types. The solid electrolyte layer may contain a composite solid electrolyte comprising an inorganic solid electrolyte and a polymer electrolyte.

[0044] The solid electrolyte layer may contain a liquid electrolyte (electrolyte) along with the solid electrolyte. For example, the solid electrolyte layer may contain an electrolyte in an amount of less than 10% by mass relative to the total amount of electrolyte.

[0045] If the solid-state battery of this disclosure includes an electrolyte solution as the electrolyte, the type of electrolyte solution is not particularly limited, and known electrolyte solutions can be used. Specific examples of electrolytes include liquids obtained by dissolving lithium salts such as LiPF6 and LiFSi in an organic solvent. Specific examples of organic solvents include cyclic or linear carbonates such as ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). The solvent may be a mixture of two or more solvents, or a mixture containing both cyclic and linear carbonates. The solvent may contain additives such as vinylene carbonate (VC).

[0046] (Exterior) The solid-state battery of this disclosure may further include an outer casing. The outer casing houses an electrode laminate comprising at least a current collector, an electrode layer, and a solid electrolyte layer. Examples of outer casings include laminate-type outer casings and case-type outer casings. A laminate-type outer casing may be formed from a laminate (laminate film) having a metal layer containing a metal such as aluminum and a heat-seal layer containing a resin that melts upon heating.

[0047] (Restraining member) The battery of this disclosure may further include a restraining member. The restraining member applies restraining pressure in the thickness direction to the electrode stack described above. The restraining pressure applied in the thickness direction of the electrode stack may be, for example, 0.1 MPa or more, 1 MPa or more, or 5 MPa or more. The restraining pressure applied in the thickness direction of the electrode stack may be, for example, 100 MPa or less, 50 MPa or less, or 20 MPa or less.

[0048] (Applications of solid-state batteries) The applications of the solid-state batteries of this disclosure are not particularly limited. Typical applications include power sources for vehicles, electronic equipment, and electric storage systems. Of these, the batteries of this disclosure are preferably used as power sources for vehicles, and more preferably as power sources for hybrid vehicles, plug-in hybrid vehicles, or electric vehicles. Examples of vehicles include electric four-wheeled vehicles, electric two-wheeled vehicles, gasoline-powered vehicles, and diesel-powered vehicles. Examples of electric four-wheeled vehicles include battery electric vehicles (BEVs), plug-in hybrid electric vehicles (PHEVs), and hybrid electric vehicles (HEVs). Examples of electric two-wheeled vehicles include electric motorcycles and electric-assist bicycles.

[0049] <Method of manufacturing solid-state batteries> One embodiment of this disclosure is, The method for manufacturing a solid battery as described above in this disclosure, The process involves forming a negative electrode layer on a solid electrolyte layer, which includes a negative electrode active material in the form of a composite of multiple particles and a solid electrolyte. The method for forming the negative electrode layer is a method for manufacturing a solid battery, which includes applying pressure to the negative electrode layer such that at least some of the particles contained in the composite are separated from the composite.

[0050] According to the method of this disclosure, a solid-state battery can be manufactured in which the junction between the negative electrode layer and the solid electrolyte layer is well maintained.

[0051] In the method of this disclosure, the magnitude of the pressure applied to the negative electrode layer is not particularly limited, as long as it is large enough to separate at least some of the particles contained in the composite from the composite. In the method of this disclosure, the particles separated from the composite by applying pressure to the negative electrode layer are not coated with the solid electrolyte. Therefore, according to the method of this disclosure, a state in which the particles separated from the composite are invaginated into the solid electrolyte layer can be easily obtained.

[0052] In the method of this disclosure, the method of applying pressure to the negative electrode layer may be a process for transferring the negative electrode layer to the solid electrolyte layer, or a process performed on the negative electrode layer formed on the solid electrolyte layer.

[0053] The solid-state battery manufactured by the method of this disclosure may be a solid-state battery including a positive electrode center stacked structure. That is, the method of this disclosure is Forming positive electrode layers on both sides of the positive electrode current collector, Forming a solid electrolyte layer on the positive electrode layer, The process may include, in this order, forming a negative electrode layer on the solid electrolyte layer.

[0054] According to the above method, a solid-state battery can be manufactured that includes a positive electrode center stacked structure and maintains a good junction between the negative electrode layer and the solid electrolyte layer. In the above method, the method for forming the positive electrode layer, the solid electrolyte layer, and the negative electrode layer is not particularly limited and can be selected from coating methods, transfer methods, etc. There are no particular restrictions on the method used to carry out each of the above steps; methods such as coating and transfer can be selected. [Explanation of Symbols]

[0055] 30: Solid electrolyte layer 40: Negative electrode layer 42A, 42B: Particles of the negative electrode active material 44: Solid electrolyte

Claims

1. It includes a negative electrode layer and a solid electrolyte layer adjacent to the negative electrode layer, The negative electrode layer comprises a negative electrode active material and a solid electrolyte. A solid-state battery in which the negative electrode active material comprises a composite containing a plurality of particles and particles not included in the composite, wherein at least a portion of the particles not included in the composite are invaginated in the solid electrolyte layer.

2. The solid battery according to claim 1, wherein the negative electrode active material contains the element Si.

3. A solid-state battery according to claim 1 or claim 2, comprising a structure in which a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector are arranged in this order on both sides of a positive electrode current collector.

4. A method for manufacturing a solid battery according to any one of claims 1 to 3, The process involves forming a negative electrode layer on a solid electrolyte layer, which includes a negative electrode active material in the form of a composite of multiple particles and a solid electrolyte. A method for manufacturing a solid battery, comprising applying pressure to the negative electrode layer such that at least a portion of the particles contained in the composite separate from the composite, for the purpose of forming the negative electrode layer.

5. Forming positive electrode layers on both sides of the positive electrode current collector, Forming a solid electrolyte layer on the positive electrode layer, A method for manufacturing a solid battery according to claim 4, comprising, in this order, forming a negative electrode layer on the solid electrolyte layer.

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